CVE-2018-13084 in Good Time Coin
Summary
by MITRE
The mintToken function of a smart contract implementation for Good Time Coin (GTY), an Ethereum token, has an integer overflow that allows the owner of the contract to set the balance of an arbitrary user to any value.
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Analysis
by VulDB Data Team • 02/24/2020
The vulnerability identified in CVE-2018-13084 represents a critical integer overflow flaw within the mintToken function of the Good Time Coin (GTY) smart contract deployed on the Ethereum blockchain. This vulnerability stems from improper input validation and arithmetic handling within the contract's code, creating a scenario where the contract owner can manipulate user balances arbitrarily. The flaw manifests when the mintToken function processes token minting operations without adequate overflow checking, allowing for mathematical operations that exceed the maximum value representable by the underlying data types. Such vulnerabilities are particularly dangerous in decentralized applications where trustless execution is expected, as they fundamentally compromise the integrity of the tokenomics and user asset management.
The technical implementation of this vulnerability places the contract owner in a privileged position where they can exploit the integer overflow to manipulate token balances in ways that bypass normal contract logic. When the mintToken function attempts to increment user balances, the lack of proper overflow detection allows for wraparound behavior where large values can cause the balance to reset to zero or become negative, creating opportunities for malicious manipulation. This type of vulnerability falls under CWE-190, Integer Overflow or Wraparound, which specifically addresses situations where integer arithmetic operations produce results that exceed the maximum value that can be represented by the data type. The vulnerability is particularly insidious because it allows for arbitrary balance manipulation rather than just a simple overflow, giving the contract owner complete control over user token holdings.
The operational impact of this vulnerability extends far beyond simple balance manipulation, as it fundamentally undermines the trust model of the token ecosystem. Users who hold GTY tokens become vulnerable to immediate loss of funds when the contract owner exploits this flaw, as the owner can set any user's balance to zero or to extremely high values that may cause system-wide instability. The vulnerability also creates potential for denial of service scenarios where users may be unable to access their tokens or where the contract's overall functionality becomes compromised. From an attack perspective, this vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter, as it allows for the execution of arbitrary code through contract manipulation, and T1499.004 for Network Denial of Service, as it can cause system instability through malicious balance manipulation. The financial implications are severe, as this vulnerability could result in immediate loss of user funds and complete erosion of confidence in the token's integrity.
Mitigation strategies for this vulnerability require immediate code review and contract redeployment with proper integer overflow protection mechanisms. The most effective approach involves implementing comprehensive input validation and using safe arithmetic libraries that prevent overflow conditions. Smart contract developers should employ constructs such as OpenZeppelin's SafeMath library or similar implementations that automatically check for overflow conditions before performing arithmetic operations. Additionally, regular security audits and formal verification of smart contract code should be implemented to prevent similar vulnerabilities from being introduced. The contract owner should also implement access controls that limit the mintToken function to only authorized entities and consider using multi-signature wallets for operations that could affect token distribution. From a defensive perspective, users should avoid interacting with the vulnerable contract until proper patches are deployed, and monitoring systems should be established to detect unusual balance manipulations that may indicate exploitation of this vulnerability.